The present invention relates to fuser members useful in electrostatographic reproducing apparatuses, including digital, image on image, and contact electrostatic printing and copying apparatuses. The present fuser members may be used as fuser members, pressure members, transfuse or transfix members, and the like. In an embodiment, the fuser members comprise an outer layer comprising a polymer and having thereon, a liquid release agent. In embodiments, the release agent is an amino functional siloxane release agent. In embodiments, the amino-functional siloxane release agent comprises a pendant functional amino group. In embodiments, more than one amino-functional release agent is used as a blend.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member, and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles and pigment particles, or toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support, which may be the photosensitive member itself, or other support sheet such as plain paper.
The use of thermal energy for fixing toner images onto a support member is well known. To fuse electroscopic toner material onto a support surface permanently by heat, it is usually necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner material cools, solidification of the toner material causes the toner material to be firmly bonded to the support.
Typically, the thermoplastic resin particles are fused to the substrate by heating to a temperature of between about 90° C. to about 200° C. or higher depending upon the softening range of the particular resin used in the toner. It may be undesirable to increase the temperature of the substrate substantially higher than about 250° C., because of the tendency of the substrate to discolor or convert into fire at such elevated temperatures, particularly when the substrate is paper.
Several approaches to thermal fusing of electroscopic toner images have been described. These methods include providing the application of heat and pressure substantially concurrently by various means, a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, a belt member in pressure contact with a heater, and the like. Heat may be applied by heating one or both of the rolls, plate members, or belt members. The fusing of the toner particles takes place when the proper combinations of heat, pressure and contact time are provided. The balancing of these parameters to bring about the fusing of the toner particles is well known in the art, and can be adjusted to suit particular machines or process conditions.
During operation of a fusing system in which heat is applied to cause thermal fusing of the toner particles onto a support, both the toner image and the support are passed through a nip formed between the roll pair, or plate or belt members. The concurrent transfer of heat and the application of pressure in the nip affect the fusing of the toner image onto the support. It is important in the fusing process that no offset of the toner particles from the support to the fuser member takes place during normal operations. Toner particles offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thus increasing the background or interfering with the material being copied there. The referred to “hot offset” occurs when the temperature of the toner is increased to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member. The hot offset temperature or degradation of the hot offset temperature is a measure of the release property of the fuser roll, and accordingly it is desired to provide a fusing surface, which has a low surface energy to provide the necessary release. To ensure and maintain good release properties of the fuser roll, it has become customary to apply release agents to the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, nonfunctional silicone oils or mercapto- or amino-functional silicone oils, to prevent toner offset.
U.S. Pat. No. 4,029,827 discloses the use of polyorganosiloxanes having mercapto functionality as release agents.
U.S. Pat. No. 4,101,686 to Strella et al. and U.S. Pat. No. 4,185,140 also to Strella et al., both disclose polymeric release agents having functional groups such as carboxy, hydroxy, epoxy, amino, isocyanate, thioether, or mercapto groups.
U.S. Pat. No. 5,157,445 to Shoji et al. discloses toner release oil having a functional organopolysiloxane of a certain formula.
U.S. Pat. No. 5,395,725 to Bluett et al. discloses a release agent blend composition wherein volatile emissions arising from the fuser release agent oil blend are reduced or eliminated.
U.S. Pat. No. 5,512,409 to Henry et al. teaches a method of fusing thermoplastic resin toner images to a substrate using amino functional silicone oil over a hydrofluoroelastomer fuser member.
U.S. Pat. No. 5,516,361 to Chow et al. teaches a fusing member having a thermally stable FKM hydrofluoroelastomer surface and having a polyorgano T-type amino functional oil release agent. The oil has predominantly monoamino functionality per active molecule to interact with the hydrofluoroelastomer surface.
U.S. Pat. No. 5,531,813 to Henry et al. discloses a polyorgano amino functional oil release agent having at least 85% monoamino functionality per active molecule to interact with the thermally stable FKM hydrofluoroelastomer surface of the fuser member.
U.S. Pat. No. 5,698,320 discloses the use of fluorosilicone polymers for use on fixing rollers with outermost layers of perfluoroalkoxy and tetrafluoroethylene resins.
U.S. Pat. No. 5,716,747 discloses the use of fluorine-containing silicone oils for use on fixing rollers with outermost layers of ethylene tetrafluoride perfluoro alkoxyethylene copolymer, polytetrafluoroethylene and polyfluoroethylenepropylene copolymer.
U.S. Pat. No. 5,747,212 to Kaplan et al. discloses an amino functional oil having a formulation set forth in the patent.
U.S. Pat. No. 6,183,929 B1 to Chow et al. discloses a release agent comprising (a) an organosiloxane polymer containing amino-substituted or mercapto-substituted organosiloxane polymers, wherein the amino or mercapto functional groups on at least some of the polymer molecules having a degree of functionality of from about 0.2 to about 5 mole percent, and (b) a nonfunctional organosiloxane polymer having a viscosity of from about 100 to about 2,000 centistrokes, and wherein the mixture has a degree of functionality of from about 0.05 to about 0.4 mole percent.
The use of polymeric release agents having functional groups, which interact with a fuser member to form a thermally stable, renewable self-cleaning layer having good release properties for electroscopic thermoplastic resin toners, is described in U.S. Pat. No. 4,029,827.
In high-speed color fusing applications, adequate coverage of the fuser member surface is required to meet the demanding environmental conditions and exposure to various levels of toner materials and additives, rapid high temperature thermal cycling and various media composition and weights. Amino silicone release agents are typically used in such high-speed color fusing systems, due to their ability to sufficiently react with the fluoroelastomer surface coatings that are used in conventional fuser member component compositions. In maintaining a printing system level balance and reliability among the fuser member coating properties, paper properties, toner composition and image content it is necessary to utilize a release fluid that is robust against average customer document job mix failures modes as well as specific stress cases that result in failure modes that render the fuser member unusable and thus increase costs of operations and ownership.
Several specific examples of these catastrophic failure modes are outlined herein. A stripping failure in an electrophotographic fusing system is defined as a failure where the paper leaving the exit nip of the fuser is still adhered to the roll surface, resulting in the paper following the fuser surface back around rather than freely leaving the nip. This failure is caused by a failure of the release agent to split within the layer applied to the fuser member surface or by toner on the imaged page contacting the fuser member surface; resulting in adhesive forces holding the imaged page to the member as the sheet passes through the nip. This results in the paper being heated too long, the toner in contact with the fuser member surface for an extended period of time and potential non-recoverable jam situations that render the fuser member unusable beyond this particular failure mode. Offset failures in high-speed color fusing are characterized by a gradual build-up of un-transferred or unreleased residual toner and built-up gelation of oil over the course of several thousand copies. It is observed under different image densities and conditions than stripping failures, and also results in a catastrophic failure for the fuser member. As copy count increases and material from gelled fuser oil and toner continue to accumulate on the fuser surface, the material eventually builds up to such a level that it transfers back to subsequent images, resulting in a noticeable print quality defect. The location of the built up material on the roll will continue to transfer a defect to prints and is difficult to remove, thus rendering the fuser member unusable after the point of failure. Accelerated testing can be performed for each of these failure modes. In some cases, the offset stripping defect will occur in the stripping stress test. In most cases, however, each accelerated stress test will only exhibit a catastrophic failure in the failure mode it is testing for. Thus it is possible that silicone release agents possessing different structures, methods of making, and compositions, could be useful for mitigating each of the respective defects in high-speed color fusing applications.
In addition, some print quality defects are observable in high-speed color applications that render the print objectionable to the customer. One example of a print quality defect, although there are several, is denoted as wavy gloss. Wavy gloss is a print quality defect that exhibits random variable gloss levels within a single imaged sheet. The defect can appear and disappear, but occurs to varying levels depending on the nature and composition of the release fluid.
There are three major failure modes of the high-speed full process color fusing namely stripping, hot offset and wavy gloss. The first two impact the fuser reliability, which is basically fuser life and paper jamming. The third failure mode results into image quality defects due to differential gloss. Differential gloss is a phenomenon that occurs when there is a noticeable difference in the gloss levels between different spots within a single image/page. Normally, this is associated with characteristic wear patterns or other artifacts on the fuser roll or other hardware. Differential gloss typically appears in a stark delineation in appearance. The wavy gloss is wavy, or in other words, the width and length of the pattern on the image is variable and not delineated, as in most typical differential gloss print artifacts.
Therefore, for polymeric outer layers, including fluoroelastomeric fuser member outer layers, there exists a specific need for a release agent, which provides sufficient wetting of the fuser member. It is further desired to provide a fuser member release agent, which has little or no interaction with copy substrates such as paper, so that the release agent does not interfere with adhesives and POST-IT® notes (by 3M) adhering to the copy substrate such as paper. It is further desired that the oil not prevent ink adhesion to the final copy substrate. In addition, it is desired that the release agent does not react with components of the toner. It is also desired to provide an amino-functional release agent decreases or eliminates gelation. Also, it is desired to provide a release agent that enables increase in life of the fuser member by improved spreading of the release agent. A further desired feature is to provide a fuser release agent increases life of the fuser member by decreasing offset failure and stripping failures, reducing paper jams, and improving overall image quality.